Nothing happens when using 3DPrint
When you use the Check All button (or any other test) in the Print3D panel of the toolbar (visible by pressing T) you will see a list at the bottom of the panel listing the number of affected parts for each test.

While in edit mode this list becomes buttons for any items that exist. Clicking a button will select the particular areas.



The coloured areas you see in the above image are from another related feature called Mesh Analysis, this feature highlights the affected areas and can be activated in edit mode from the properties panel (visible by pressing N).